With cerise lips and auburn hair, crimson cloak and tunic, and details on his armour picked out in maroon and electric blue, Caesar Augustus raises his right hand in the air. He resembles, as the art historian Fabio Barry unhappily commented to the Washington Post in 2008, ‘a cross-dresser trying to hail a taxi’. Is this really what Rome’s first emperor was supposed to look like? The coloured reconstruction in plaster of Paris, made by Vatican conservators in 2004, radically transforms the Prima Porta statue of Augustus. The original Parian marble work, from around the start of the first century CE, is one of the masterpieces of the Vatican Museums. There, it stands within a conventionally pallid gallery of unpainted Roman statues and busts. But the classical whiteness of ancient sculpture is an illusion. It has been known for more than two centuries that Greek and Roman artists routinely added pigments both to statues and architecture. The acknowledgement of their use on ancient Greek temples like the Parthenon inspired the bright, variegated decoration of Greek Revival architecture in 19th-century Europe. Occasionally, ancient sculptures themselves bear extant traces of paint. When the Prima Porta statue was excavated on the site of the Empress Livia’s villa near Rome in 1863, some of its colours were still visible to the naked eye. Not long afterwards, new archaeological discoveries in Greece – particularly the archaic sculptures of the Athenian Acropolis – seemed to prove that at least some ancient marbles were as brightly painted as Mediterranean fishing boats.

Nevertheless, academic awareness of polychromy has never much penetrated popular consciousness of ancient art; nor, indeed, has it shaped research. Only in recent years has scholarship on the subject blossomed, notably with a groundbreaking scientific project at the Ny Carlsberg Glyptotek in Copenhagen and with touring exhibitions of astonishing plaster reconstructions by the German archaeologist Vinzenz Brinkmann. It was in the context of Brinkmann’s 2003 exhibition at the Glyptothek in Munich, ‘Gods in Colour’, that a team at the Vatican subjected the Prima Porta statue to scientific analysis, identifying the pigments that had apparently vanished since the sculpture’s discovery. Visitors to Brinkmann’s iconoclastic exhibitions are invariably shocked and delighted. Yet, we should be cautious about such reconstructions. Notwithstanding the gamut of scientific imaging techniques available to modern research, a lot of speculation is employed to fill the gaps. Reconstructions in plaster hardly do justice to the marble originals. There are good reasons to believe that colour was a much more subtle component of many ancient sculptures than the eye-catching re-creations imply. The Romans, for example, conceived of portraits as true likenesses. To leave them unpainted would have been as senseless as presenting white waxworks in Madame Tussauds. For the same reason, however, garish colours would have undermined their evocative purpose.

Perhaps, though, our biggest obstacle is an insurmountable one. Reconstructing the colour of ancient sculpture can jolt us into re-imagining a world that differs from our expectations, but ancient viewers took polychromy for granted and, therefore, literally saw it in a different way. We can never view these colours through their eyes.

Dr Peter Stewart is Director of the Classical Art Research Centre and Associate Professor of Classical Art and Archaeology at Oxford University, UK. His books include Statues in Roman Society: Representation and Response (2003) and The Social History of Roman Art (2008).